Methods and apparatus for single fiber optical telemetry

Abstract

Single fiber optical telemetry systems and methods are disclosed. The methods and systems facilitate input and output via a single fiber optic interface. The optical telemetry systems and methods also facilitate faster data transmission rates between surface and downhole equipment in oilfield applications.

1. An optical telemetry system, comprising:
 a downhole oilfield tool; 
 only a single optical fiber extending between a surface location and the downhole oilfield tool, the single optical fiber terminating at and coupled to a substrate, the substrate comprising at least two optical paths; 
 a plurality of electrodes connected to the substrate for modulating light passing through the optical paths, wherein the substrate comprises lithium niobate with Ti diffused therein to define said optical paths; 
 an optical circulator downstream of the substrate; and 
 an optical bypass fiber extending from the optical circulator, wherein the modulated light passes through the optical circulator, the bypass fiber, and into the single optical fiber. 
 
   
   
     2. The system of  claim 1 , wherein the substrate, optical paths, and electrodes comprise an electro-optic modulator. 
   
   
     3. The system of  claim 2 , wherein the electro-optic modulator comprises a light intensity modulator. 
   
   
     4. The modulator of  claim 1 , further comprising a polarizer coupled upstream to the optical paths. 
   
   
     5. The system of  claim 1 , wherein the substrate, optical paths, and electrodes comprise an electro-absorption modulator. 
   
   
     6. An electro-optical modulator comprising:
 a downhole lithium niobate with Ti diffused therein substrate; 
 at least two waveguides disposed in the substrate; 
 an optical input/output comprising a single fiber coupled to the waveguides; and 
 a plurality of electrodes arranged about the waveguides for modulating light passing through the waveguides; 
 an optical circulator downstream of the substrate; and 
 an optical bypass fiber extending from the substrate to the optical coupler, wherein the modulated light passes through the optical circulator, the bypass fiber, and into the single fiber fiber. 
 
   
   
     7. The modulator of  claim 6 , wherein the optical bypass fiber comprises an optical path independent of the waveguides. 
   
   
     8. The modulator of  claim 6 , wherein the single fiber comprises a polarization maintaining fiber. 
   
   
     9. The modulator of  claim 8 , wherein the single fiber is rotated an odd multiple of approximately 45 degrees with respect to the waveguides. 
   
   
     10. A downhole telemetry system comprising:
 a surface data acquisition unit comprising a surface optical telemetry unit; 
 a downhole optical telemetry cartridge comprising a downhole electro-optic unit; and 
 a single-fiber optical interface between the surface data acquisition unit and the downhole optical telemetry cartridge, 
 wherein the downhole optical telemetry cartridge comprises an external electrical-to-optical modulator, comprising: 
 a downhole substrate comprising lithium niobate with Ti diffused therein; 
 at least two waveguides disposed in the substrate; 
 an optical input/output comprising a single fiber terminating at and coupled to the waveguide; 
 an optical circulator disposed downstream of the waveguides; 
 a plurality of electrodes arranged about the waveguides for modulating light passing through the waveguides; and 
 an optical bypass fiber extending from the downhole substrate to the single fiber, wherein the modulated light passes through the optical circulator, the bypass fiber, and into the input fiber. 
 
   
   
     11. The system of  claim 10 , further comprising an optical source only at the surface. 
   
   
     12. The system of  claim 10 , wherein the external electrical-to-optical modulator comprises an electro-absorption modulator. 
   
   
     13. The system of  claim 10 , wherein the external electrical-to-optical modulator comprises a single-fiber input/output medium. 
   
   
     14. The system of  claim 10 , and further comprising a polarization maintaining fiber rotated an odd multiple of approximately 45 degrees from the axes of the waveguides. 
   
   
     15. A method of communication between a surface location and one or more downhole tools, comprising:
 receiving electrical signals from the one or more downhole tools; 
 modulating light by the electrical signals from the one or more downhole tools, the modulating comprising:
 receiving light from a surface location source via an input fiber of a downhole electrical-to-optical modulator; 
 passing the light through at least two waveguides disposed in a substrate having a plurality of electrodes for modulating light passing through the waveguides said substrate comprises lithium niobate with Ti diffused therein; 
 modulating the light; 
 outputting the modulated light back through the input fiber; 
 receiving and detecting the modulated light at the surface location, wherein the outputting the modulated light back through the input fiber comprises passing the modulated light through an optical circulator in a first direction, redirecting the modulated light through an optical bypass fiber for bypassing the waveguides, and inserting the modulated light back into the input fiber. 
 
 
   
   
     16. The method of  claim 15 , wherein the outputting the modulated light back through the input fiber comprises directing the modulated light with an optical circulator, wherein the optical circulator is located upstream of the electrical-to-optical modulator. 
   
   
     17. The method of  claim 15 , wherein the modulating comprises changing the intensity of the light received from the surface location with an external electrical-to-optical modulator located downhole. 
   
   
     18. The method of  claim 15 , wherein the modulation further comprises applying a changing voltage across the waveguides. 
   
   
     19. The method of  claim 15 , wherein:
 the receiving light from a surface location source via the input fiber further comprises passing the light through an optical circulator upstream of the at least two waveguides disposed in the lithium niobate with Ti diffused therein substrate and passing the light into the waveguides; 
 the modulating the light further comprises applying a voltage across the waveguides; and 
 the outputting further comprises directing the modulated light exiting the waveguides back to the optical circulator via a continuing fiber.